1. Field of the Invention
The present invention relates to a shutter opening device for a disk cartridge receiving an information recording medium such as an optical disk or an optomagnetic disk.
2. Related Background Art
As shown in FIG. 1, a conventional shutter opening device for such a disk cartridge (to be simply referred to as a cartridge hereinafter) containing an optomagnetic disk comprises a cartridge 2 containing a disk-like recording medium 1 and having a shutter 3, a cartridge holder (to be simply referred to as a holder hereinafter) 4 which is vertically moved between an inserting position (upper position) at which the cartridge 2 is horizontally inserted from a direction indicated by an arrow a, and a loading position (lower position) at which the disk-like recording medium 1 in the inserted cartridge 2 is loaded on a disk table, a pivot arm 5 mounted on the holder 4 to be pivoted about a fulcrum 4a in directions indicated by arrows b and b', a pin 7 vertically provided on the distal end of the pivot arm 5 and serving as an ejection means, and a spring 6 for biasing the pivot arm 5 in the direction indicated by the arrow b'.
The cartridge 2 is loaded in the following manner. When the cartridge 2 is horizontally inserted into the holder 4 in the direction indicated by the arrow a, the pin 7 is pushed by a leading portion 2a of the cartridge 2 and is pivoted about the fulcrum 4a by the pivot arm 5 in the direction indicated by the arrow b against the biasing force of the spring 6. As a result, a side surface portion 3a of the shutter 3 is pushed by the pin 7 to open the shutter 3 in a direction indicated by an arrow c against the biasing force of a spring (not shown) incorporated in the shutter 3. Thereafter, the pin 7 is caused to retreat into a recess 2b formed in the leading portion 2a of the cartridge 2, so that the pin 7 is locked between the side surface portion 3a of the shutter 3 and the recess 2b. A trigger arm 10 is then pivoted about a fulcrum 11 by the leading portion 2a of the cartridge 2 in a direction indicated by an arrow f against the biasing force of a spring 12 immediately before the cartridge 2 is completely inserted in the holder 4 and the cartridge leading portion 2a is brought into contact with a bent portion (stopper) 4b formed on the holder 4. As a result, the holder 4 is moved downward to the loading position, thus completing the loading operation.
When the cartridge 2 is to be ejected, the holder 4 is completely moved upward from the loading position to the inserting position to release the lock. The cartridge leading portion 2a is slightly pushed in the direction indicated by the arrow a' by the trigger arm 10 which is pivoted about the fulcrum 11 in a direction indicated by f' by the spring 12, thus withdrawing the pin 7 from the cartridge recess 2b onto the leading portion 2a. Subsequently, the cartridge leading portion 2a is pushed by the pin 7 which is pivoted about the fulcrum 4a in the direction indicated by the arrow b' by the spring 6 upon operation of the pivot arm 5. As a result, the cartridge 2 is ejected from the holder 4 in the direction indicated by the arrow a' while the shutter 3 is closed in a direction indicated by an arrow c' by the built-in spring.
FIG. 2 shows another conventional shutter opening device for a cartridge containing a floppy disk. This device is almost the same as the one shown in FIG. 1, which is designed for an optomagnetic disk, except that a fulcrum 4a is formed outside the loading position of a cartridge 2 (behind the loading position), and the shutter is opened while the pivot arm 5 is pushed.
In the conventional device shown in FIG. 1, since the fulcrum 4a is located above the cartridge 2, the pivot arm 5 overlaps the cartridge 2. Similarly, the spring 6 for biasing the pivot arm 5 overlaps the cartridge 2 regardless of whether the spring 6 is a coil or torsion spring. This makes it difficult to realize a low-profile shutter opening device.
In the conventional device shown in FIG. 2, which is designed for a floppy disk, since the pivot arm 5 is located outside the cartridge 2, the pivot 5 and the spring 6 do not overlap the cartridge 2. This allows the formation of a flat structure and hence realizes a low-profile device. However, such a structure is only allowed for a floppy disk but cannot be applied to an optomagnetic disk. This is because an optomagnetic disk requires a larger opening in the cartridge than a floppy disk because of the structure of a recording/reproducing head, and the stroke of movement of the shutter 3 of the device for the optomagnetic disk is larger than that of the device for the floppy disk. More specifically, the initial position of the side surface portion (driving point) 3a of the shutter 3 is located near the side surface portion of the cartridge 2. Consequently, a moment angle 8 of the pivot arm 5 is increased, and the pivot arm 5 cannot be pivoted. The moment angle 8 is an angle defined by a vector d of movement of the pin 7 (pivot arm 5) and the inserting direction. As the moment angle .theta. is decreased, the shutter is opened more easily. When the angle is 90.degree., the shutter cannot be opened A moment angle .theta.b of the pivot arm 5 for the floppy disk can be set to be 60.degree. or less. In this case, when the cartridge 2 is inserted, the pin 7 or the pivot arm 5 can be sufficiently pivoted by the cartridge leading portion 2a. A moment angle .theta.a of the pivot arm 5 for the optomagnetic disk shown in FIG. 1 is about 45.degree.. If a fulcrum 4a' is arranged outside the cartridge 2, as shown in FIG. 2, a moment angle .theta.a' is close to 90.degree.. Therefore, when the cartridge 2 is inserted, the cartridge leading portion 2a and the pivot arm 5 push each other, and the pivot arm 5 cannot be pivoted. In order to increase the moment angle .theta.a', the fulcrum 4a' must be arranged outside the holder 4 or the pivot arm 5 must be extremely elongated.